This invention relates to an apparatus for fusion-splicing a pair of polarization maintaining optical fibers and, more particularly, to an improvement on a mechanism for aligning a pair of polarization maintaining optical fibers with each other when the optical fibers are fusion-spliced.
In aligning a pair of polarization maintaining optical fibers to be fusion-spliced with each other, the optical fibers must be moved not only in X and Y directions (those are oriented orthogonally on the cross sections of the optical fibers), but also in the circumferential direction. As shown in FIGS. 1 and 2, each of a pair of polarization maintaining optical fibers comprises cores 14, cladding region 16, and stress-applying parts 18. FIGS. 1 and 2 only show the portions of the optical fibers, which are adjacent to the to-be-fusion-spliced end faces of the fibers. These figures show the cross sections of the fibers, thereby to facilitate the understanding of the structure of the optical fibers, although actually they cannot be seen since the fibers are positioned face-to-face. The remaining portion of each fiber is covered with sheath laid around and in contact with cladding region 16. The exposed portion of each fiber where the sheath is peeled off will be referred to as an exposed fiber portion 12. The portion covered with sheath will be referred to as a sheathed fiber portion 11 (not shown in FIGS. 1 and 2). The entire optical fiber will be referred to as optical fiber 10.
In aligning a pair of polarization maintaining optical fibers with each other, in order to minimize the extinction ratio, stress-applying parts 18 of one of the fibers are, as shown in FIG. 1, aligned with those of the other fiber, or are, as shown in FIG. 2, displaced in maximum from those of the other fiber.
In both cases, the optical fibers must be moved in X and Y directions so as to obtain the axial alignment of the fibers. These directions are orthogonally oriented to each other on the cross sections of the fibers.
Further, the fibers are turned by angle .theta. in a circumferential direction around the axes of the fibers, i.e., the Z-axis to align respective the stress-applying parts 18 of the fibers or to displace the parts in maximum.
Practically, however, it is very difficult to turn the optical fibers finely in the circumferential direction so that the stress-applying parts may be aligned or displaced in maximum.